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Biomedical subjects

C P Lin

Publications and source records attributed to C P Lin.

At least 55 records · Page 3Linked to original sources
PubMed1999

The merit of sintered PDLLA/TCP composites in management of bone fracture internal fixation.

Polyesters based on lactic acid have been reported in terms of safety and biodegradation in human beings for 2 decades. The greatest advantage of such material is its degradation conducted only by hydrolysis, whereby the ester backbones are supposed to be unchained in the aqueous condition. The final degradable products are carbon dioxide and water which can be metabolized and digested in the physiological environment. The goal of this study was aimed at developing a composite sintered with poly-DL-lactide (PDLLA) and tricalcium phosphate (TCP) ceramic particles for orthopedic application. The TCP particles in a range of 30-60 wt% with 5 wt% increments were doped into the PDLLA matrix which was prepared by melting and hot pressing techniques for the reinforcement. The basic mechanical strength, biodegradable behavior, and biological response of the composites were investigated in the study. Various techniques such as pH meter, UV, Fourier-transform infrared, and x-ray diffractometer were used to examine and record the degradable process of the composites soaked in saline for 1-16 weeks. The rabbit femur condyle fracture fixation test was used to evaluate tissue compatibility and the effects of bone fracture fixation on the composites. Histological observation and x-ray photography were used for investigating assistance. The mechanical strength of the composites initially increased with TCP additions up to 50wt%, but thereafter they showed no significant difference (p < 0.05). The composite with 50 wt% TCP addition showed greater mechanical strength and had good agreement with cortical bone in terms of its elastic modulus of 30-40 GPa. The weight loss of the pure PDLLA soaked in the saline started at 4 weeks and reached 95% after 16 weeks. The composites compared with pure PDLLA, however, showed no apparent evidence of degradation after soaked for 12 weeks. The possible mechanisms for the delayed degradation of the composites in saline might have been solution penetration retardation by the ceramic particles and chemical bonds formed between the interface of the TCP particles and the PDLLA matrix. In the histological evaluation of the rabbit femur condyle fracture fixation test, the surface of the composite with 50 wt% TCP addition was attached by the newly generated bone without fibrous tissue around 8 weeks after implantation. The fractured bone was gradually healed and the composite firmly and properly fixed on the fracture area during the implanted period, which provided a breeding environment for normal bone remodeling. The developed composite was thought to be an alternative material for orthopedic application in the future, especially for bone screws and bone plates.

Absorption↗
PubMed1999

Toxic effects of mitomycin-C on cultured corneal keratocytes and endothelial cells.

Improper use of mitomycin-C in ocular medication may result in damage to corneal cells. In this study, the toxic effects of mitomycin-C on cultured porcine keratocytes and endothelial cells were estimated by MTT, 3H-thymidine uptake and cellular counting assay methods. It was found that mitomycin-C caused a dose-dependent toxic effect to keratocytes and endothelial cells. Both cells were treated with mitomycin-C at the concentration ranging from 100, 10, 1, 0.1 to 0.01 microg/ml for 3 min, 5 min or 100 min. The 50% inhibitory dose (ID50) of mitomycin-C to keratocytes and endothelial cells as measured by MTT assay was 0.40, 0.18, 0.16 mg/ml and 0.27, 0.15, 0.14 mg/ml, respectively, after 3, 5 and 100 minutes drug treatment. The ID50 for keratocytes and endothelial cells as measured by 3H-thymidine uptake immediately, 1 day and 7 days after 100 minutes mitomycin-C treatment was 0.3, 0.0002, 143.2 microg/ml and 45.1, 101.1, 450.2 microg/ml, respectively. The ID50 for keratocytes and endothelial cells as measured by cellular counting 1 day and 7 days after mitomycin-C treatment was 232.5, 109.7 microg/ml and 239.9, 367.5 microg/ml, respectively. It is concluded that mitomycin-C is more toxic to cellular proliferation in cultured corneal keratocytes than in endothelial cells.

Animals↗
PubMed1999

Influences of methylcellulose on corneal epithelial wound healing.

We performed a study to evaluate the influence of methylcellulose (MC) on the corneal epithelial wound healing. A precise epithelial wound 2.0 mm in diameter and 70 microm in depth was created by an excimer laser on the cornea of a pig's eyeball. After treatment, the eyeballs were cultured in the incubator and perfused with TC-199 medium into the vitreous cavity. Topical MC with eight different combinations of concentrations and viscosities for experimental groups and BSS for the control group were applied on the epithelial defects three times. Wounds were evaluated 24 hours later with fluorescein stain and recorded with a scoring system. All of the experimental groups except one showed a more statistically significant superior wound-healing rate than the control group. MC possesses the effect to accelerate corneal epithelial wound healing.

Animals↗
PubMed1999

Fungal corneal ulcers of onion harvesters in southern Taiwan.

Fungal corneal ulcers related to agriculture has been reported throughout the world, especially in tropical areas. Most of them were sporadic and had histories of ocular trauma or use of topical corticosteroids and topical antibiotics. Five onion harvesters had fungal corneal ulcers during the same harvest period in Southern Taiwan. The authors think that this is the first report of a group occurrence relating to agricultural workers. Although all of the patients improved after medical and surgical management, their vision was greatly decreased. It is suggested that the tropical climate, the harvest procedure, the characteristic monsoon, and lack of eye protection were involved. Therefore, the importance of the eye protection, hygiene education, and improving medical care to reduce the occurrence of fungal corneal ulcer in agriculture workers must be emphasised.

Adult↗
PubMed1999

Progressive outer retinal necrosis syndrome as an early manifestation of human immunodeficiency virus infection.

Progressive outer retinal necrosis syndrome is a recently recognized variant of necrotizing herpetic retinopathy, developing in patients with acquired immune deficiency syndrome (AIDS) or other conditions causing immune compromise. We report a case in which the diagnosis of retinal necrosis syndrome was made before the diagnosis of AIDS was confirmed. A 41-year-old man presented with a 1-month history of blurred vision in his left eye. Ophthalmologic examination revealed extensive retinal necrosis with total retinal detachment in his left eye and multifocal deep retinal lesions scattered in the posterior fundus as well as in the peripheral retina in his right eye. The serologic test for human immunodeficiency virus (HIV) was positive. Despite intravenous acyclovir treatment for 1 week, the lesions in the right eye showed rapid progression. High doses of intravitreal ganciclovir were then given in addition to intravenous acyclovir. After combined treatment for 1 month, the lesions became quiescent and the visual acuity improved to 20/30. Although the patient soon developed full-blown AIDS, the vision in his right eye remained undisturbed. Physicians should suspect progressive outer retinal necrosis syndrome in any patient with rapidly progressive necrotizing retinopathy and test the patient for HIV infection. Aggressive combined antiviral agent therapy should be considered to save vision.

AIDS-Related Opportunistic Infections↗
PubMed1999

Stability of self-prepared fortified antibiotic eyedrops.

Self-prepared fortified antibiotic eye drops are essential for the severe ocular infection. The relation of potency decay and storage conditions including temperature, concentration and duration were studied by the changes of MIC. 1% and 10% amikin, 10% and 50% pipril, and 5% and 25% vancomycin were diluted from the prarenteral antibiotics with the 5% glucose and storage at 4, -18 and -80 degrees C for 3, 7, 14 and 28 days. MICs of amikin against Pseudomonas aeruginosa, pipril and vancomycin against Staphylococcus aureus were determined by the agar diffusion method. Fluctuations of the MIC were noted during the observation period. Most of the significant changes of MIC were found during the first 7 days. When the potencies between time of zero and 28 days are compared, only 10% pipril and 25% vancomycin stored at -80 degrees C had significant change. Our conclusion is that all of the fortified antibiotic eye drops in this study can be stored in the house refrigerator or freezer for up to 28 days. High concentration may show a negative result of the preservation. Temperature does not influence the preservative effect within four weeks' observation.

Anti-Bacterial Agents↗
PubMed1999

Intraocular use of fluconazole in the management of ocular fungal infection.

In this study, we investigate the efficacy and safety of intraocular use of fluconazole in the treatment of ocular fungal infection. Ten patients with intraocular fungal infections were examined. Among these patients, eight were infected with keratomycosis with intraocular spreading, one had postoperative fungal endophthalmitis after cataract operation with an intraocular lens implant, and another suffered from endogenous fungal endophthalmitis. In addition to the conventional local application with or without systemic administration of antifungal drugs, all ten patients were treated with intraocular administration of 5-10 micrograms/ml of fluconazole. The ocular fungal infections resolved in nine patients without obvious side effect. One failed in the antifungal treatment with loss of vision. In our experience, the results revealed that fluconazole is a safe and effective antifungal agent that can be administered intraocularly. We suggest that intraocular administration of this drug could be considered as an alternative or additional choice for the treatment of severe ocular fungal infections.

Adult↗
PubMed1999

Ultrastructural changes of the tooth root surface by Nd:YAG laser irradiation followed by citric acid and tetracycline.

The neodymium:yttrium-aluminum-garnet (Nd:YAG) laser has been used for treatment of dentinal hypersensitivity, eradicating periodontal pathogens, and facilitating calculus removal. However, Nd:YAG laser irradiation exerts potentially harmful effects on the tooth root surface. The purpose of this study was to examine the ultrastructural changes of the tooth root surface caused by Nd:YAG laser irradiation, and to determine whether chemical and mechanical preparations can correct these ultrastructural changes. Eighteen tooth specimens (3 x 3 x 0.5 mm) with healthy root surfaces were prepared and irradiated with an Nd:YAG laser at various power densities. Root surfaces were irradiated at 100 mJ at 20 pulses per second (pps) for 2 seconds followed by the application of citric acid (pH 1.2) or tetracycline solution (100 mg/mL) for 3 and 5 minutes, respectively, or ultrasonic scaling for 5 strokes of 3 seconds per stroke. As observed with low-vacuum scanning electron microscopy, (Wet-SEM), Nd:YAG laser irradiation at 70 to 100 mJ, 20 pps for 2 seconds caused surface cratering, areas of porosity, pitting, fissures, and lava-like structures in an area 140 to 280 microns in diameter. Irradiation of 50 mJ, 20 pps for 2 seconds, led to only mild surface charring. No evidence of morphologic changes was found when root surfaces were irradiated with the Nd:YAG laser at 20 mJ, 20 pps for 2 seconds or at 50 mJ, 10 pps for 8 seconds. The laser-induced lava-like structures were partially detached by citric acid (pH 1.2) etching and ultrasonic scaling, but not by tetracycline (100 mg/mL). These results indicate that chemical and mechanical preparations can be used effectively in conjunction with Nd:YAG laser irradiation for root surface preparation during both nonsurgical and surgical periodontal treatments.

Anti-Bacterial Agents↗
PubMed1999

Treatment of dental root fracture by medium energy CO2 laser and DP-bioactive glass paste. Part. II: Compositional, structure, and phase changes of DP-bioglass paste after exposed to CO2 laser.

Fractured teeth are difficult to treat effectively. Currently, such as root fractures are usually treated by full-coverage restoration, root amputation, or tooth extraction. If the fusion of tooth fracture by laser were possible, it could offer a different therapy to repair fracture teeth. We tried to use a developed DP-bioactive glass paste to fuse or bridge the tooth crack line by a medium energy continuous-wave CO2 laser. The present report was focused on the phase transformation and rescrystallization of DP-bioactive paste during expose to the CO2 laser. The materials will examine by means of XRD, FTIR, DTA/TGA, and SEM. From the study, we could expect that the temperature increase due to laser irradiation must be over than 900 degrees C and the DP-bioactive glass paste could be melted in a short period of time after irradiation. In the study, we successfully developed a DP-bioactive glass paste which could form a melting glass within minutes after exposed to a medium energy density continuous-wave CO2 laser. The paste will be used to bridge the enamel or dentine surface crack by the continuous-wave CO2 laser in the near future.

Dental Cements↗
PubMed1998

17beta-estradiol inhibition of ascorbic acid accumulation in human intestinal Caco-2 cells.

We investigated the effect of estrogen on the accumulation of ascorbic acid by human intestinal Caco-2 cells. 17beta-estradiol, synthetic estrogen diethylstilbestrol, and partial agonist tamoxifen were found to inhibit ascorbic acid accumulation in a dose-dependent fashion. The inhibitory effect of estrogens can be observed at as short as 5 min of incubation. An additive effect was observed when they were used in combination. Similar to dietary flavonoids, inhibition was also observed in two other intestinal cell lines, HT-29 and IEC-6. These chemicals affected both Na+ -dependent and Na+ -independent(K+ substituting Na+) accumulation of ascorbic acid and did not affect the efflux of accumulated ascorbic acid. Kinetic analysis of diethylstilbestrol showed a non-competitive inhibition with an apparent Ki of 23 microM. The hormone-ascorbic acid interaction in the intestinal cell could help to explain the known reduction in blood ascorbic acid level among oral contraceptive users and female guinea pigs given contraceptive hormones.

Ascorbic Acid↗
PubMed1998

Dietary flavonoids interact with trace metals and affect metallothionein level in human intestinal cells.

Flavonoids are natural compounds found in food items of plant origin. The study examined systematically the interaction of structurally diverse dietary flavonoids with trace metal ions and the potential impact of dietary flavonoids on the function of intestinal cells. Spectrum analysis was first performed to determine flavonoid-metal interaction in the buffer. Among the flavonoids tested, genistein, biochanin-A, naringin, and naringenin did not interact with any metal ions tested. Members of the flavonol family, quercetin, rutin, kaempferol, flavanol, and catechin, were found to interact with Cu(II) and Fe(III). On prolonged exposure, quercetin also interacted with Mn(II). Quercetin at 1:1 ratio to Cu(II) completely blocked the Cu-dependent color formation from hematoxylin. When quercetin was added to the growth medium of cultured human intestinal cells, Caco-2, the level of metal binding antioxidant protein, metallothionein, decreased. The effect of quercetin on metallothionein was dose- and time-dependent. Genistein and biochanin A, on the contrary, increased the level of metallothionein. The interaction between dietary flavonoids and trace minerals and the effect of flavonoids on metallothionein level imply that flavonoids may affect metal homeostasis and cellular oxidative status in a structure-specific fashion.

Cadmium↗
PubMed1998

The quality of ultrasonic root-end preparation: a quantitative study.

Ultrasonic root-end preparation techniques have recently been introduced and revolutionized the field of endodontic surgery. The purpose of this study was to compare quantitatively the quality of root-end preparation techniques prepared by a specially designed ultrasonic retrotip with those prepared in a traditional manner by a microhandpiece bur. Twenty roots with two canals and an isthmus from extracted maxillary human molars were selected for this study. After instrumentation, obturation, and root-end resection, root-end preparations were made using either an ultrasonic retrotip or a conventional microhandpiece bur. With the aid of the image processing and analysis system, the specimens were inspected under a stereomicroscope for further evaluation of the quality of the shape and size of preparation. The results of this investigation showed that the ultrasonic root-end preparations produced more conservative and less perforated cavities than those made with conventional microhandpiece bur preparations.

Evaluation Studies as Topic↗
PubMed1998

Vertical root fracture in nonendodontically treated teeth--a clinical report of 64 cases in Chinese patients.

Vertical root fractures (VRFs) in teeth without endodontic treatment are uncommon. A clinical study was done on 64 cases of VRFs in 61 Chinese patients to define better the clinical characteristics, diagnostic signs, and possible causes. Results showed that fractures occurred most often in first molars of patients between 40 and 69 yr of age, and the incidence was two times higher in males than in females. Flat roots with smaller mesiodistal diameters were more prone to fracture. The majority (79%) of patients had intact dentition with less than four teeth missing. Fractured teeth were frequently attrited with no restorations. VRFs may result from excessive or repetitive masticatory force due to damaging chewing habits exerted on flat roots of smaller mesiodistal diameter. Nonendodontic VRFs seem to occur more frequently than earlier believed and may represent an underdiagnosed clinical entity deserving of our attention.

Adult↗
PubMed1998

Thrombin-induced DNA synthesis of cultured human dental pulp cells is dependent on its proteolytic activity and modulated by prostaglandin E2.

To clarify the roles of alpha-thrombin and prostaglandin E2 (PGE2) in the healing and inflammatory processes of dental pulp, their effects on the DNA synthesis of human pulp cells were investigated by measurement of [3H]thymidine incorporation. At a concentration range of 1 to 25 units/ml, alpha-thrombin stimulated DNA synthesis of the pulp cells by 1.5 to 2.6-fold. On the contrary, PGE2 (> 0.05 microgram/ml) suppressed DNA synthesis by 24 to 39%. Using reverse transcriptase-polymerase chain reaction, thrombin receptor mRNA expression was identified in the pulp cells. Furthermore, alpha-thrombin-induced DNA synthesis could be inhibited by antithrombin III (2 units/ml) with heparin (2 units/ml) or D-Phe-Pro-ArgCH2Cl (50 micrograms/ml). PGE2 (0.1 to 0.5 microgram/ml) also inhibited the thrombin-induced DNA synthesis by 39 to 64%. These results imply that pulp cells express the thrombin receptor that is activated by the serine protease activity of thrombin. Interactions of thrombin and PGE2 are important in modulating the inflammatory and healing processes of the pulp.

Cells, Cultured↗
PubMed1998

Serine protease activity is essential for thrombin-induced protein synthesis in cultured human dental pulp cells: modulation roles of prostaglandin E2.

Irritations and injuries to the dental pulp usually lead to different degrees of pulpal inflammation. To investigate the roles of thrombin and prostaglandins in the healing and inflammatory processes of dental pulp as well as their effects on pulpal protein synthesis, human dental pulp cell cultures were established and their protein production was measured with or without the presence of exogenous thrombin and prostaglandins. At concentrations of 1-25 U/ml, alpha-thrombin increased the protein synthesis to 1.4-2.3 fold over the vehicle control. On the contrary, 0.1 microg/ml of prostaglandin E1 (PGE1) suppressed protein synthesis by 60%. Prostaglandin E2 (PGE2) also inhibited protein synthesis with an IC50 of 0.4 microg/ml. The stimulatory effects of thrombin (10 U/ml) can be inhibited by antithrombin III (2 U/ml) (a natural thrombin inhibitor) with heparin (2 U/ml), PPACK (D-Phe-Pro-ArgCH2Cl) (20-50 microg/ml) (a serine protease inhibitor), and PGE2 (0.5-1.0 microg/ml). Moreover, TRAP (20-40 microg/ml), a thrombin receptor agonist peptide, also exerted a stimulatory effect (1.21-1.37 fold). In conclusion, thrombin-induced protein synthesis by pulp cells is dependent on proteolytic activity, but not on binding to receptors. Both PGE1 and PGE2 exert suppressive effects on protein synthesis, indicating that interactions between thrombin and prostaglandins are important in regulating the inflammation, repair and regeneration of pulp tissue following injury.

Adult↗
PubMed1998

The deafness-associated mitochondrial DNA mutation at position 7445, which affects tRNASer(UCN) precursor processing, has long-range effects on NADH dehydrogenase subunit ND6 gene expression.

The pathogenetic mechanism of the deafness-associated mitochondrial DNA (mtDNA) T7445C mutation has been investigated in several lymphoblastoid cell lines from members of a New Zealand pedigree exhibiting the mutation in homoplasmic form and from control individuals. We show here that the mutation flanks the 3' end of the tRNASer(UCN) gene sequence and affects the rate but not the sites of processing of the tRNA precursor. This causes an average reduction of approximately 70% in the tRNASer(UCN) level and a decrease of approximately 45% in protein synthesis rate in the cell lines analyzed. The data show a sharp threshold in the capacity of tRNASer(UCN) to support the wild-type protein synthesis rate, which corresponds to approximately 40% of the control level of this tRNA. Strikingly, a 7445 mutation-associated marked reduction has been observed in the level of the mRNA for the NADH dehydrogenase (complex I) ND6 subunit gene, which is located approximately 7 kbp upstream and is cotranscribed with the tRNASer(UCN) gene, with strong evidence pointing to a mechanistic link with the tRNA precursor processing defect. Such reduction significantly affects the rate of synthesis of the ND6 subunit and plays a determinant role in the deafness-associated respiratory phenotype of the mutant cell lines. In particular, it accounts for their specific, very significant decrease in glutamate- or malate-dependent O2 consumption. Furthermore, several homoplasmic mtDNA mutations affecting subunits of NADH dehydrogenase may play a synergistic role in the establishment of the respiratory phenotype of the mutant cells.

Base Sequence↗
PubMed1998

Keratomycosis with an unusual clinical manifestation--a case report.

We report a case of keratomycosis which had recurrent, deep stromal infiltration and an endothelial plaque for half a year after the original corneal foreign body injury. The subject had an unusual clinical picture of deep corneal infiltration and later hair-like material growing from the endothelial plaque into the anterior chamber. Repeated corneal scrapings for smears and cultures all showed negative during the initial treatment. We tried anterior chamber paracentesis and endothelial aspiration and got a positive finding of Cladosporium infection. This case is presented because of the difficulty of diagnosis and management of fungal keratomycosis.

Cladosporium↗